In the rapidly advancing world of semiconductor device manufacturing, semiconductor fin devices such as FinFET (fin Field Effect Transistor) and other devices are becoming favored because of the increased levels of integration and increased miniaturization that they enable. Fin devices typically involve a narrow, tall semiconductor fin formed over a substrate which may be a semiconductor substrate or an insulating substrate and provide the advantage that a transistor gate formed using the fin utilizes the sides and top of the fin for current flow thereby providing a gate width that may be magnitudes greater than the gate width of a transistor formed directly on the substrate, and improving device speed. The source and drain of such a transistor are also formed along the fin device.
Like conventional transistors formed in the substrate surface, the semiconductor material that forms the fin may be subjected to the introduction of dopant impurities therein, as the semiconductor surfaces of the fin serve as the channel, and the source and drain along which current flows, for FinFET transistor devices. The introduction of such dopant impurities typically occurs using ion implantation. An example of one such implantation process is an LDD, lightly doped drain, implant used to introduce dopant impurities in the form of ions, into the surfaces of the semiconductor fins by way of ion implantation. Angled ion implantation processes are available for such implanting operations, but the ability to thoroughly and uniformly implant the sides of the fins to provide a desired, uniform dopant profile, is limited by the high aspect ratios and tightly packed nature of the semiconductor fins, and further limited by the masking material, typically patterned photoresist, used to isolate the fins being implanted as well as the proximity to other types of fins which are not desired to be implanted. One type of fin (e.g. fins used for N-type devices) is typically implanted while fins of the other type (e.g. fins used for P-type devices) are covered with a masking material to prevent them from being implanted. Conventional methods do not provide a sufficiently high implant angle to completely, thoroughly and uniformly introduce dopant impurities into the sides of the semiconductor fins to provide a uniform dopant distribution. This limitation is illustrated in FIG. 1, which is indicative of conventional processing.
FIG. 1 shows substrate 101 which includes semiconductor fins 105, 107 formed over surface 103. Semiconductor fins 105 may represent fins of a first type used for a particular application and/or possessing a particular characteristic, e.g., for N-type transistors, whereas semiconductor fins 107 may represent fins of a second type used for different applications and/or having different characteristics, e.g., such as for P-type transistors. Semiconductor fins 105 are processed separately from semiconductor fins 107 and are spaced apart by separation distance 161.
FIG. 1 illustrates a conventional example in which photoresist pattern 109 is formed to cover semiconductor fins 107 while semiconductor fins 105 undergo an implantation processing operation. Photoresist pattern 109 includes edge 123 which is generally spaced about halfway between semiconductor fins 107 and semiconductor fins 105 in conventional technology. The implantation processing operation is designed to implant dopant species in the form of energized ions into sides 119 and top 121 of semiconductor fins 105 while semiconductor fins 107 are covered and not subjected to the ion implantation process. The angled implantation process is represented by parallel arrows 113 indicating the implant direction. It can be seen that implant angle 117 is limited by the presence and proximity of photoresist pattern 109 which covers semiconductor fins 107, thereby preventing the introduction of the dopant impurities into covered semiconductor fins 107. Photoresist pattern 109 covers and extends laterally past the semiconductor fins 107. It would be desirable to increase the implant angle 117 for any given thickness 111 of photoresist pattern and for any given separation distance 161 between semiconductor fins 105 and semiconductor fins 107, to more completely, thoroughly and uniformly introduce dopant impurities into the semiconductor fins.
The present invention addresses these limitations.